Hey alaphoid, first let me thank you for picking up one of our engines. Now as to the shimming question this is really one of those type of questions where if you got to ask you should probably not be doing it. Shimming to adjust deck height is a pretty important and I should say exact thing that should not be taken lightly. Doing it incorrectly or should I say setting it too low will (and there is no maybe, it will) result in detonation and damage to your engine. When adjusting deck height every set up is unique and is predominately dictated by the atmospheric conditions & elevation, heat range of the plug, pipe choice and very importantly (and often forgotten) the fuel composition that is used.

If you are comfortable adjusting deck height through trial and error (slowly lowering it and checking for signs of detonation and continuing to do so until you do) then by all means go for it. If you are not comfortable doing this then I would recommend that you just leave deck height where it is and run 30% fuel which the engine is set up for from the factory.

Regards,

Ron